Elastomeric roof sheeting, also referred to as roofing membranes, are known for use as roofing materials, particularly as single ply rubber roofing membranes for industrial and commercial flat roofs. These membranes are generally applied to the roof surface in the vulcanized or cured state. Elastomers which are most commonly employed in forming the membranes are EPDM, butyl and neoprene, but chlorosulfonated polyethylene and chlorinated polyethylene are occasionally utilized in some special applications. The roofing membranes are generally prepared by calendering the unvulcanized elastomer compounds into sheets of various widths, lengths and thickness and then vulcanizing the sheets usually employing hot air or steam autoclave, although continuous vulcanization is reported to be beyond the research phase.
Elastomeric roof flashing is also known for its use on roofs, especially flat roofs. This material is employed to seal around elements that extend or protrude from the roof surface such as sky lights, air conditioning units, vent pipes and the like. The elastomeric flashing compound is often formulated using the same elastomers as are employed in the roof sheeting compound, but a special curing package is included in the compound which allows it to cure over an extended period of time under ambient temperature conditions. Thus, the roof flashing is applied to the roof surface in the unvulcanized state and cures in-situ on the roof.
Vulcanizable elastomeric EPDM and butyl compositions containing conventional carbon blacks, fillers and vulcanizing agents have long been known in the tire and industrial rubber products arts.
More recently, vulcanizable EPDM and/or butyl rubber compositions have been proposed for use as roof sheeting and flashing materials as illustrated by U.S. Pat. Nos. 4,461,875 and 4,514,442. The aforementioned patents relate to roof sheeting and flashing compositions which comprise an elastomer selected from the group consisting of EPDM, butyl rubber and an EPDM-butyl rubber mixture; from 0.1 to 3.0 parts of a compound having the structural formula [(CH.sub.2).sub.n NCS].sub.2 S.sub.6 wherein n is 4 or 5; and 0 to 5.0 parts of a sulfur donor curative. The patents further disclose that the compositions may additionally contain one or more vulcanizing accelerators, processing oils, plasticizers, fillers and reinforcing agents. Among the fillers and reinforcing agents which are said to be especially useful are carbon black, silicates, talc, calcium carbonate and the like.
Single-ply EPDM membranes of the type previously described are generally singular formula, homogeneous, membrane types that may contain fire retardant chemical formulations (sometimes referred to as fire retardant membranes) or they may not contain such chemicals and are known as standard EPDM membranes. In either case, the entire membrane thickness is of the same material composition. Both types of membranes are in commercial use.
The standard (non-fire retardant) prior art membranes of singular homogeneous materials have relied on subsequently applied coatings of a fire retardant nature to enable standard EPDM membranes to pass all Class A and B ASTM E 108 (UL-790) testing. These coatings degrade in time and if not replaced, result in loss of fire retardancy. The composite of this invention is a unitary, singular product that will perform equal to the noted coated product, but will neither degrade nor require replenishment to maintain its fire retardancy.
The composite of this invention, relative to a single ply 100% fire retardant membrane now in commercial use, has the following advantages:
(1) Cost; PA1 (2) Greater tensile strength; PA1 (3) Enhanced aging properties; PA1 (4) Increased adhesion when the two plies are calendered into a single sheet; PA1 (5) Equivalent fire retardancy in some roofing assemblies; and PA1 (6) Improved factory seam strength.
Thus, the prior art has not successfully produced the fire retardant composite roofing material of the present invention, as evidenced by the following prior art patents:
Draexler, U.S. Pat. No. 4,551,392, discloses a composite material layer which comprises two distinct layers, a first layer in the form of an EPDM or EPM elastomeric composition, and a second layer of a different elastomeric component. The second layer can have, e.g., a flame retardant property (col. 1, line 14).
Bulgin, U.S. Pat. No. 2,341,360, discloses a fire resistant electrically conductive rubber article which is used in the flooring of hospital rooms and which was designed to prevent the accumulation of static charges of electricity as well as ignition of the floor. As a result, a two-layer composite having a flame retardant lower rubber layer 10 and a rubber mix in the form of an upper layer 11 rendered conductive by being compounded with conductive materials is shown. A layer of fire resistant electrically conductive rubber layer is calendered into sheets and is applied in an unvulcanized state to a calendered sheet formed of rubber and several incombustible substances.
Lonning, U.S. Pat. No. 3,549,474, discloses a fire retardant insulation material which can comprise a low density batt and an organic facing layer. This insulation comprises a facing layer 11 and a batt 13 attached to each other by an intermediate layer of adhesive 12. Each facing layer is said to have excellent fire retardancy, low temperature flexibility and adequate tensile strength properties.
Stamper, et al., U.S. Pat. No. 4,515,744, discloses a laminate of fused vinyl chloride polymer plastisols which can be used as a roofing membrane. The outer layer includes titanium dioxide to improve weather resistance, and the inner layer an effective amount of a fire retardant material, e.g., Sb.sub.2 O.sub.3.
Schoenke, U.S. Pat. No. 4,032,491, claims a roofing membrane formed from a composition which can include, e.g., conventional additives such as fire retardants. Similarly, Tierney, U.S. Pat. No. 4,000,140, discloses a waterproof roofing layer in the form of a sheet comprising a bitumen, a synthetic polymer, and a particulate filler; a fire retardant additive may also be included in the mixture.
Yost, U.S. Pat. No. 4,172,179, discloses a flame retardant plastic laminate which comprises a core section 2 and at least one facing or cladding section 3, although a second such section can be added. The plastic core section 2 can be formed from non-flame retardant polypropylene and a layer of flame retardant plastic material, e.g., polypropylene layer 4, can be attached thereto.
Windecker, U.S. Pat. No. 3,493,460, discloses a fire retardant laminate which comprises a first facing sheet or skin 11 and a fire retardant thermoset resin matrix 12 attached thereto. A core 24 is disposed between faces 21 and 14 of respective elements 17 and 11, which core adheres to the faces via a thermoset resin, e.g., matrix 25 of core 24 comprises a thermoset fire retardant synthetic resin.
Haage, et al., U.S. Pat. No. 3,992,842, discloses, as illustrated in FIG. 1a, a composite sheet having an upper thermoplastic cover layer 1a, a lower thermoplastic cover layer 1b, and an intermediate flameproofing layer 2. The flameproofing layer can be, e.g., inorganic fiber such as fiberglass or asbestos. Two abutting composite sheets of synthetic resin are abutted by solution welding, hot air welding or gluing. The sheet is used for sealing roofs.